1. Field of the Invention
The disclosure relates in general to a liquid crystal display (LCD) with shifted pixels, and more particularly to a naked-eye three-dimensional (3D) LCD with shifted pixels.
2. Description of the Related Art
Being compact in size, light in weight, power-saving and radiation-free, liquid crystal displays (LCDs) are prevalent in diversified applications from small-sized portable information products such as personal digital assistants (PDAs), medium-sized LCD monitors of laptop computers or desktop computer monitors, to large-sized 30 to 50-inch LCD televisions. LCDs are in fact an essential part of the daily life electronic products.
By offering a wide viewing angle in an LCD, an observer may perceive images having small color and brightness differences when observing the LCD from a frontal viewing angle and from side viewing angles. The effect can be achieved through enhancing the quality of side-viewing-angle images by forming a multi-domain in a single sub-pixel region. Various types of wide angle techniques are available, from which three types namely vertical alignment (VA), in-plane switching (IPS)/fringe-field switching (FFS), and twisted nematic (TN) cooperating a wide-angle compensation film are most well-known. An LCD based on vertical alignment includes multi-domain vertical alignment (MVA) having protrusions, and pattern vertical alignment (PVA) that does not have protrusions and forms multiple slits on a transparent electrode (e.g., indium tin oxide (ITO) on a color filter (CF)). The presence of the protrusions and slits cause a pre-tilted angle in liquid crystal molecules and thus tilted electric fields. In PVA, an aperture can be increased to further enhance the brightness without incurring a severe issue of dark-state light leakage as that caused by conventional MVA. In the recently developed polymer stabilization alignment (PSA), a small amount of monomer is added to liquid crystal molecules, and a voltage is applied after injecting the liquid crystals to produce a pre-tilted angle for the liquid crystal molecules near a region of the polyimide. With appropriate exposure to UV light, the pre-tilted angle is stabilized while also completing polymer stabilization and liquid crystal alignment. Accordingly, PSA is capable of mitigating the dark-state light leakage issue and further enhancing contrast.
Further, a rubbing or non-rubbing technique may be implemented in an alignment process of an alignment film at an inner side of upper and lower substrates (e.g., a TFT substrate and a CF substrate), so that liquid crystal molecules may align according to a predetermined direction and a predetermined tilt angle regardless of whether electric fields are present to achieve multi-domain alignment. For example, the non-rubbing technique includes ion beam alignment, plasma alignment and photo-alignment (PA). The non-rubbing technique is increasingly drawing attention as it solves issues of electrostatic electricity and dust pollution. The PA approach among the non-rubbing technique is based on triggering optical anisotropy by radiating an alignment film with polarized UV light. In a manufacturing process of the PA approach, an alignment material (e.g., a photosensitive polymer) is applied to a glass substrate such as a TFT substrate and a CF substrate followed by applying UV light radiation, such that photopolymerization, isomerization and cracking are incurred at the polymer structure of the alignment film. Thus, a special directionality is produced in bond structures at a surface of the alignment film and is automatically guided into a radiation angle of the UV light, so as to further cause the pre-tilted angle of the liquid crystal molecules in the liquid crystal layer to automatically align along the direction of the macromolecules of the polymer of the alignment film.
Displays such as liquid crystal displays (LCDs) have been developed to provide three-dimensional (3D) displays in various kinds of displays. Currently, most of 3D displays require the use of special headgear or glasses and provide the 3D displaying effect for users. Due to inconveniency of the use of headgear or glasses, many manufacturers have been studied and advanced towards the technology of autostereoscopic display.
Autostereoscopic displays, also known as “Naked eye 3D display”, are able to provide binocular depth perception without the hindrance of specialized headgear or filter/shutter glasses. Naked eye 3D displays have been demonstrated using a range of optical elements in combination with an LCD including parallax barrier technology and lenticular optic technology to provide stereoscopic vision. Generally, the parallax barrier has optical apertures aligned with columns of LCD pixels, and the lenticular optics has cylindrical lenses aligned with columns of LCD pixels. A parallax barrier could be a sheet or an electro optic panel with fine slits to separate the light pathway of spatial images into images for left eye and right eye, and this reconstructed scene of the left eye image and right eye image is perceived as 3D images by the observer. FIG. 1 is a conventional 3D display with parallax barrier. A parallax barrier 15 is positioned in front of a display panel 11, and between human eyes and the display panel 11. The backlight module 13 emits light. The parallax barrier 15 with transparent and opaque strips limits the pixels only radiate light in directions seen by the left eye or right eye. In the accurate alignment between the backlight module 13 and the display panel 11, the left eye and the right eye of the observer would receive images on the odd numbered pixels and even numbered pixels, respectively. When different images are presented on the odd numbered pixels and even numbered pixels of the display panel 11 and received by the left eye and the right eye correspondingly, it is capable of providing depth perception and stereoscopic vision to the viewer. Alternatively, the parallax barrier 15 could be positioned behind the display panel 11, and between the backlight module 13 and the display panel 11. The transparent and opaque strips of the parallax barrier 15 are still able to partially block the light emitted from the backlight module 13 and only transparent strips allow penetration of light, thereby achieving the 3D displaying effect without glasses.
In a conventional naked-eye 3D LCD, multiple rectangular sub-pixels are aligned in a matrix arrangement. A barrier with grating stripes, formed by perpendicularly alternate transparent slits and opaque shields of a barrier, is placed on the display panel which displays a pattern for image fusion, and the direction of the slits is perpendicular to the direction of the rectangular sub-pixels. However, the above arrangement likely causes a Moire Effect to human eyes. On the other hand, if the slits are arranged relative to the sub-pixels by a tilted angle, crosstalk between images can easily be resulted. FIG. 2 shows a top view of pixels and a parallax barrier of a display module in a conventional naked-eye 3D LCD. A display module 21 includes a plurality of pixels, each having at least three differently-colored sub-pixels 22, e.g., red, green and blue sub-pixels. In FIG. 2, an example of the naked-eye 3D LCD having six viewing positions is depicted, i.e., R1 to R6 respectively represent the red sub-pixels at first to sixth viewing angles correspondingly. Transparent slits 251 on a barrier 25 are disposed at a tilted angle relative to the red, green and blue sub-pixels. As shown in FIG. 2, crosstalk is resulted since regions of the transparent slits 251 also include parts of adjacent images of the sub-pixels 22 that do not correspond to a same viewing position.